Ribbon bonding tools and methods of using the same

ABSTRACT

A ribbon bonding tool including a body portion is provided. The body portion includes a tip portion. The tip portion includes a working surface between a front edge of the tip portion and a back edge of the tip portion. The working surface includes a region defining at least one of a plurality of recesses and a plurality of protrusions. The working surface also defines at least one of (a) a first planar portion between the region and the front edge of the tip portion, and (b) a second planar portion between the region and the back edge of the tip portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/705,341, filed May 6, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/378,421, filed Jan. 10, 2013, which claims thebenefit of U.S. patent application Ser. No. 13/145,676, filed Jul. 21,2011, which claims the benefit of International Patent Application No.PCT/US2010/023273 filed Feb. 5, 2010, which claims the benefit of U.S.Provisional Application Nos. 61/150,633; 61/150,596; 61/150,611;61/150,625; 61/150,579; and 61/150,640, each of which was filed Feb. 6,2009, the contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to bonding tools used in ribbon bondingsystems, and more particularly, to improved tip portions of ribbonbonding tools.

BACKGROUND OF THE INVENTION

In the processing and packaging of semiconductor devices, wire bondingcontinues to be a primary method of providing electrical interconnectionbetween two locations within a package (e.g., between a die pad of asemiconductor die and a lead of a leadframe). To form wire loops toprovide this interconnection, bonding tools (e.g., capillary tools usedduring ball bonding, wedge tools used in wedge bonding) are used topress a wire against a bonding location using ultrasonic, thermosonic,or thermocompressive energy.

In the assembly of certain devices (e.g., power semiconductor devices)ribbon bonding may be used to provide electrical interconnection betweenlocations. For example, U.S. Patent Application Publication Nos.2006/0163315 (entitled Ribbon Bonding Tool and Process) and 2007/0141755(entitled Ribbon Bonding in an Electronic Package) relate to ribbonbonding and are incorporated herein by reference.

Various of the drawings disclosed herein (e.g., FIGS. 1, 2, and 3A-3F)are useful in explaining conventional ribbon bonding tools and systems,as well as ribbon bonding tools and systems according to the presentinvention. FIG. 1 illustrates semiconductor die 110 supported bysubstrate 108 (e.g., leadframe 108). It is desired to provide aconductive interconnection between a location(s) on semiconductor die110 (e.g., a die pad) and lead 108 a of leadframe 108. Ribbon loop 112provides such interconnection and includes first bond 112 a and secondbond 112 b (both bonded to portions of semiconductor die 110), as well athird bond 112 c on lead 108. Ribbon loop 112 is formed using ribbonbonding system 100 (e.g., a ribbon bonding machine). As is understood bythose skilled in the art, a ribbon bonding system includes manyconventional components and subsystems such as a material handlingsystem, a vision system, a computer, and many others. However, forsimplicity, only a few elements of ribbon bonding system 100 are shown.Such elements include ribbon bonding tool 102, ribbon guide 104, andcutting tool 106. During formation of ribbon loops (such as ribbon loop112) a ribbon material is fed to ribbon bonding tool 102 from a ribbonsupply (not shown) using ribbon guide 104. Ribbon bonding uses energy(e.g., ultrasonic energy to form bonds), and then, after formation of aribbon loop, cutter 106 may be used to at least partially cut throughthe ribbon material prior to separation of the ribbon loop from theribbon supply.

FIG. 2 is a perspective view of ribbon bonding tool 102 engaged inaperture 114 a of ultrasonic transducer 114, where ribbon bonding tool102 is aligned in aperture 114 a using flat surface side 102 k (in thiscase, front side 102 k). As is understood by those skilled in the art,transducer 114 causes a “scrubbing” motion at the tip portion 102 a, andparticular, to working surface 102 b of ribbon bonding tool 102. FIGS.3A-3F are various views of exemplary ribbon bonding tool 102. FIG. 3A isa front view of tool 102, FIG. 3B is a top view of tool 102(illustrating flat surface side 102 k), FIG. 3C is a bottom viewillustrating working surface 102 b, FIG. 3D is a detailed view of aportion of FIG. 3A illustrating front edge 102 d of tip portion 102 aadjacent working surface 102 b, FIG. 3E is a side view of tool 102, andFIG. 3F is a detailed view of a portion of FIG. 3E illustrating sideedge 102 f 1 of tip portion 102 a adjacent working surface 102 b.

Certain ribbon bonding tools have features formed on the working surfacesuch as those shown in U.S. Patent Application Publication No.2006/0163315 entitled Ribbon Bonding Tool and Process. FIG. 4A is anexemplary tip portion 102 a of a conventional ribbon bonding tool 102.Tip portion includes working surface 102 b, front edge 102 d, back edge102 e, side edge 102 f 1, and side edge 102 f 2. Working surface 102 bdefines protrusions 102 b 1 and recesses 102 b 2 (where the protrusionsand recesses may be part of a waffle or grid pattern on the workingsurface), where recesses 102 b 2 are between protrusions 102 b 1. Atypical scrubbing motion of a ribbon bonding tool is from front to back,along the direction of the ribbon. In FIG. 4A, the scrubbing wouldtypically occur in direction “d” which extends in a direction from frontedge 102 d to back edge 102 e.

FIG. 4B is a perspective view of a portion of ribbon loop 112 includingfirst bond 112 a bonded to bonding location 110. First bond 112 a isformed using a “waffle” type ribbon bonding tool (similar to that shownin FIG. 4A) which forms openings/recesses 112 a 2 between protrusions112 a 1. Unfortunately, conventional waffle style ribbon bond toolssuffer from a number of deficiencies. For example, the edges of theprotrusions on the working surface of the ribbon bonding tool tend toleave an irregular edge in the heel region of the ribbon bond, which mayinitiate cracks 112 a 3 at some point during the life of the ribbonbond. Other limitations of existing ribbon bonding tools relate toribbon looping difficulties, amongst others.

Thus, it would be desirable to provide improved ribbon bonding tools.

SUMMARY OF THE INVENTION

According to an exemplary embodiment of the invention, a ribbon bondingtool including a body portion is provided. The body portion includes atip portion. The tip portion includes a working surface between a frontedge of the tip portion and a back edge of the tip portion. The workingsurface includes a region defining at least one of a plurality ofrecesses and a plurality of protrusions. The working surface alsodefines at least one of (a) a first planar portion between the regionand the front edge of the tip portion, and (b) a second planar portionbetween the region and the back edge of the tip portion.

According to another exemplary embodiment of the present invention, aribbon bonding tool including a body portion is provided. The bodyportion includes a tip portion. The tip portion includes a workingsurface between a front edge of the tip portion and a back edge of thetip portion. The working surface defines a plurality of recesses,wherein a portion of the recesses defined by the working surfaceadjacent at least one of the front edge and the back edge are deeperthan others of the recesses.

According to another exemplary embodiment of the present invention, aribbon bonding tool including a body portion is provided. The bodyportion includes a tip portion. The tip portion includes a workingsurface, wherein during engagement with a transducer of a ribbon bondingsystem, the working surface extends lower in a center region than (a) ata first surface region extending from a first edge of the workingsurface toward the center region, and (b) at a region extending from asecond edge of the working surface toward the center region, a length ofthe first surface region being at least 25% of a length of the workingsurface from the first edge to the second edge, a length of the secondsurface region being at least 25% of a length of the working surfacefrom the first edge to the second edge.

According to another exemplary embodiment of the present invention, aribbon bonding tool including a body portion is provided. The bodyportion includes a tip portion. The tip portion including a workingsurface. The tip portion includes two side wall portions on either sideof the working surface wherein a ribbon path is defined between the sidewall portions.

According to another exemplary embodiment of the present invention, aribbon bonding tool including a body portion is provided. The bodyportion includes a tip portion. The tip portion includes a workingsurface. The tip portion includes two side wall portions extending alongan exterior surface of at least a portion of a back side of the ribbonbonding tool wherein a ribbon path is defined between the side wallportions.

The inventive ribbon bonding tools may also be integrated into inventiveribbon bonding systems including various elements such as bond headelements (e.g., ultrasonic transducers, ribbon cutter, ribbon materialguides), as well as other elements.

Further, the invention may also be considered in connection with methodsof forming ribbon loops. Such methods may include a step of forming aribbon bond of a ribbon loop on a first bonding location, extending theribbon material toward a second bonding location, forming another ribbonbond on the second bonding location, and separating the now completedribbon loop from the ribbon supply (using a ribbon cutter, if desired,to assist in the separation). Such a method is accomplished using aninventive ribbon bonding tool (and other elements of a ribbon bondingsystem) according to the exemplary embodiments disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingsare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawings are the following figures:

FIG. 1 is a side block diagram view of portions of a ribbon bondingsystem useful in explaining various exemplary embodiments of the presentinvention;

FIG. 2 is a perspective view of a ribbon bonding tool engaged in atransducer useful in explaining various exemplary embodiments of thepresent invention;

FIGS. 3A-3F are various views of the ribbon bonding tool of FIG. 2;

FIG. 4A is a perspective view of a tip portion of a conventional ribbonbonding tool;

FIG. 4B is a portion of a ribbon loop formed using a conventional ribbonbonding tool;

FIG. 5A is a perspective view of a tip portion of a ribbon bonding toolin accordance with an exemplary embodiment of the present invention;

FIG. 5B is a portion of a ribbon loop formed using the ribbon bondingtool of FIG. 5A;

FIG. 6A is a perspective view of a tip portion of a ribbon bonding toolin accordance with an exemplary embodiment of the present invention;

FIG. 6B is a portion of a ribbon loop formed using the ribbon bondingtool of FIG. 6A;

FIGS. 6C-6H are perspective views of tip portions of ribbon bondingtools in accordance with various exemplary embodiments of the presentinvention;

FIG. 7A is a side view of a portion of a conventional ribbon bondingtool;

FIG. 7B is a cross sectional view of a portion of a ribbon bond formedusing the ribbon bonding tool of FIG. 7A;

FIGS. 8A-8B are perspective views of tip portions of ribbon bondingtools in accordance with exemplary embodiments of the present invention;

FIG. 9A is a side view of a portion of a ribbon bonding tool inaccordance with an exemplary embodiment of the present invention;

FIG. 9B is a cross sectional view of a portion of a ribbon bond formedusing the ribbon bonding tool of FIG. 9A;

FIG. 10A is a bottom view of a ribbon bonding tool in accordance with anexemplary embodiment of the present invention;

FIGS. 10B-10C are various cross sectional views of the ribbon bondingtool of FIG. 10A;

FIGS. 11A-11B are block diagram views of a portion of a conventionalribbon bonding tool;

FIG. 12A is a perspective view of a portion of a ribbon bonding tool inaccordance with an exemplary embodiment of the present invention;

FIG. 12B is a block diagram view of a portion of the ribbon bonding toolof FIG. 12A;

FIG. 13 is a block diagram front view of a portion of a conventionalribbon bonding tool;

FIG. 14 is a block diagram front view of a portion of a ribbon bondingtool in accordance with an exemplary embodiment of the presentinvention;

FIGS. 15A-15B are perspective views of a tip portion of a ribbon bondingtool in accordance with an exemplary embodiment of the presentinvention;

FIGS. 16A-16B are perspective views of a portion of a ribbon bondingtool in accordance with an exemplary embodiment of the presentinvention;

FIG. 17 is a perspective view of a portion of a working surface of aconventional ribbon bonding tool; and

FIG. 18 is a perspective view of a portion of a working surface of aribbon bonding tool in accordance with an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

According to certain exemplary embodiments of the present invention, theworking surface (also known as a “foot”) of a ribbon bonding toolincludes a region defining at least one of a plurality of recesses and aplurality of protrusions (such as in a waffle or grid pattern). Theworking surface also defines at least one planar portion, along at leastone edge of the working surface. FIGS. 5A, 6A, and 6C-6H illustrate anexample of such a ribbon bonding tool, with FIGS. 5B and 6B illustratingportions of ribbon loops. The planar portions may have dimensions (e.g.,width, height, etc.) that vary. The planar portions are not required tobe perfectly flat or smooth, but rather are smoother or flatter than theedges of a standard waffle tool. Such planar portions tend to improvelooping capability and reduction of crack initiation sites in the heelregion of the ribbon loop.

FIG. 5A is a perspective bottom view of tip portion 502 a of a ribbonbonding tool. Tip portion 502 a includes working surface 502 b betweenfront edge 502 d and back edge 502 e (and also defined between side edge502 f 1 and side edge 502 f 2). Working surface 502 b includes a regiondefining protrusions 502 b 1 and recesses 502 b 2 (similar to a wafflepattern). Working surface 502 b also defines first planar portion 502 g1 between the region and front edge 502 d, and second planar portion 502g 2 between the region and back edge 502 e. In contrast to conventionalwaffle tools where the entire working surface definesprotrusions/recesses, planar portions 502 g 1 and 502 g 2 leave smoothheel regions during ribbon looping with decreased potential forcrack-initiation sites. The length L1 of the first planar portion (orthe length L2 of the second planar portion) may be between 5-40 percentof the length L from front edge 502 d to back edge 502 e.

FIG. 5B illustrates a portion of ribbon loop 512 formed using the ribbonbonding tool of FIG. 5A. Portion 512 a of ribbon loop 512 corresponds tothe region of working surface 502 b including protrusions 502 b 1 andrecesses 502 b 2. More specifically, protrusions 512 b of portion 512 acorrespond to recesses 502 b 2 of working surface 502 b, and recesses512 c of portion 512 a correspond to protrusions 502 b 1 of workingsurface 502 b. Planar portions 512 d 1 and 512 d 2 correspond to planarportions 502 g 1 and 502 g 2 of working surface 502 b, and providedesirable heel regions “h” in ribbon loop 512.

In the configuration shown in FIG. 5A, the region of working surface 502b defining protrusions 502 b 1 and recesses 502 b 2 is mostly below aplane defined across planar portions 502 g 1 and 502 g 2 (i.e., the topof protrusions 502 b 1 is at substantially the same height as planarportions 502 g 1 and 502 g 2). However, the region could extend above aplane defined across planar portions 502 g 1 and 502 g 2.

Referring now to FIG. 6A, a perspective bottom view of tip portion 602 aof a ribbon bonding tool is shown. Tip portion includes working surface602 b between front edge 602 d and back edge 602 e (and also definedbetween side edge 602 f 1 and side edge 602 f 2). Working surface 602 bincludes a region defining protrusions 602 b 1. Working surface 602 balso defines first planar portion 602 g 1 between the region and frontedge 602 d, second planar portion 602 g 2 between the region and backedge 602 e, third planar portion 602 g 3 between the region and sideedge 602 f 2, and fourth planar portion 602 g 4 between the region andside edge 602 f 2. FIG. 6B illustrates portion 612 a of ribbon loop 612formed using the ribbon bonding tool of FIG. 6A. Portion 612 a includesrecesses 612 c corresponding to protrusions 602 b 1 of working surface602, and planar portions 612 d 1 and 612 d 2. FIGS. 6C-6H are similar tothe embodiment shown in FIG. 6A, where like reference numeralscorrespond to like elements of the ribbon bonding tool.

FIG. 6C illustrates tip portion 622 a including working surface 622 bbetween front edge 622 d, back edge 622 e, side edge 622 f 1, and sideedge 622 f 2. Working surface 622 b includes a region defining two rowsof diamond shaped protrusions 622 b 1. Working surface 622 b alsodefines first planar portion 622 g 1 between the region and front edge622 d, second planar portion 622 g 2 between the region and back edge622 e, third planar portion 622 g 3 between the region and side edge 622f 1, and fourth planar portion 622 g 4 between the region and side edge622 f 2. Of course, other shapes and configurations of protrusions onthe working surface are contemplated.

FIG. 6D illustrates tip portion 632 a including working surface 632 bbetween front edge 632 d, back edge 632 e, side edge 632 f 1, and sideedge 632 f 2. Working surface 632 b includes a region defining roundshaped protrusions 632 b 1. Working surface 632 b also defines firstplanar portion 632 g 1 between the region and front edge 632 d, secondplanar portion 632 g 2 between the region and back edge 632 e, thirdplanar portion 632 g 3 between the region and side edge 632 f 1, andfourth planar portion 632 g 4 between the region and side edge 632 f 2.FIG. 6E illustrates tip portion 642 a including working surface 642 bbetween front edge 642 d, back edge 642 e, side edge 642 f 1, and sideedge 642 f 2. Working surface 642 b includes a region definingrectangular shaped protrusions 642 b 1. Working surface 642 b alsodefines first planar portion 642 g 1 between the region and front edge642 d, second planar portion 642 g 2 between the region and back edge642 e, third planar portion 642 g 3 between the region and side edge 642f 1, and fourth planar portion 642 g 4 between the region and side edge642 f 2.

The features on the working surface are not limited to protrusions, butmay include recesses, or both recesses and protrusions. FIGS. 6F-6Hillustrate exemplary configurations with recesses. FIG. 6F illustratestip portion 652 a including working surface 652 b between front edge 652d, back edge 652 e, side edge 652 f 1, and side edge 652 f 2. Workingsurface 652 b includes a region defining diamond shaped recesses 652 b1. Working surface 652 b also defines first planar portion 652 g 1between the region and front edge 652 d, second planar portion 652 g 2between the region and back edge 652 e, third planar portion 652 g 3between the region and side edge 652 f 1, and fourth planar portion 652g 4 between the region and side edge 652 f 2. FIG. 6G illustrates tipportion 662 a including working surface 662 b between front edge 662 d,back edge 662 e, side edge 662 f 1, and side edge 662 f 2. Workingsurface 662 b includes a region defining round shaped recesses 662 b 1.Working surface 662 b also defines first planar portion 662 g 1 betweenthe region and front edge 662 d, second planar portion 662 g 2 betweenthe region and back edge 662 e, third planar portion 662 g 3 between theregion and side edge 662 f 1, and fourth planar portion 662 g 4 betweenthe region and side edge 662 f 2. FIG. 6H illustrates tip portion 672 aincluding working surface 672 b between front edge 672 d, back edge 672e, side edge 672 f 1, and side edge 672 f 2. Working surface 672 bincludes a region defining rectangular shaped recesses 672 b 1. Workingsurface 672 b also defines first planar portion 672 g 1 between theregion and front edge 672 d, second planar portion 672 g 2 between theregion and back edge 672 e, third planar portion 672 g 3 between theregion and side edge 672 f 1, and fourth planar portion 672 g 4 betweenthe region and side edge 672 f 2.

FIG. 7A is a side view of a portion of a conventional ribbon bondingtool with working surface 702 b having a waffle configuration, with aphantom view of a portion of working surface 702 b. Working surface 702b includes protrusions 702 b 1 (also known as teeth) and recesses 702 b2 (also known as grooves). End recesses 702 b 2 e have the same depth asother recesses 702 b 2. Thus, recesses 702 b 2/702 b 2 e across workingsurface 702 b define a groove plane GP that is substantially flat andparallel to the bottom surface (labeled as bottom surface plane BSP) ofthe ribbon bonding tool. FIG. 7B illustrates a portion of ribbon loop712 formed using the ribbon bonding tool of FIG. 7A. Ribbon loop 712includes protrusions 712 c, and recesses 712 c (where recesses 712 chave the same depth as end recesses 712 c 1).

FIGS. 8A-8B are bottom perspective views of tip portions 802 a/852 a ofribbon bonding tools according to the present invention includingrecesses of varying depths. FIG. 8A illustrates working surface 802 bincluding protrusions 802 b 1 (also known as teeth) and recesses 802 b2/802 b 2 e. End recesses 802 b 2 e along the front and back edge of tipportion 802 a are deeper than other recesses 802 b 2, thereby resultingin longer protrusions/teeth adjacent the front and back edge of tipportion 802 a. FIG. 8B illustrates working surface 852 b includingprotrusions 852 b 1 and recesses 852 b 2/852 b 2 e. End recesses 852 b 2e along the front and back edge of tip portion 852 a are deeper thanother recesses 852 b 2, thereby resulting in longer protrusions/teethadjacent the front and back edge of tip portion 852 a. The deeperrecesses along the front and back edges allow for thicker ribbonmaterial in a heel region of a ribbon loop formed using the ribbonbonding tool.

FIG. 9A is a side view of a portion of ribbon bonding tool according toan exemplary embodiment of the present invention with working surface902 b having a waffle configuration or the like, with a phantom view ofa portion of working surface 902 b. Working surface 902 b includesprotrusions 902 b 1 (also known as teeth) and recesses 902 b 2 (alsoknown as grooves). End recesses 902 b 2 e are deeper than recesses 902 b2 in the center portion of working surface 902 b. In fact, the recessesfollow a profile that is deepest at the front and back edges of workingsurface 902 b, and shallowest in a center region of working surface 902b. Thus, recesses 902 b 2/902 b 2 e across working surface 902 b definea curved groove plane GP (the groove plane GP following the shape ofworking surface 902 b at the bottom of the recesses/grooves). FIG. 9Billustrates a portion of ribbon loop 912 formed using the ribbon bondingtool of FIG. 9A. Ribbon loop 912 includes protrusions 912 b, andrecesses 912 c, 912 c 1, and 912 c 2. The center recesses 912 c areshallowest, and end recesses 912 c 2 are the deepest, with recesses 912c 1 having a depth between that of recesses 912 c and that of recesses912 c 2. Of course, protrusions 912 b will be longer where the recessesare deeper, and shorter when the recesses are shallower, therebyimproving the heel strength of the ribbon bonds formed using such atool.

FIG. 10A is a bottom view of tip portion 1002 a of a ribbon bonding toolincluding working surface 1002 b (where working surface 1002 b includesa waffle configuration including protrusions/teeth andrecesses/grooves). FIGS. 10B-10C are sectional views of the ribbonbonding tool of FIG. 10A. FIG. 10B is a sectional view cut across agroove between rows of protrusions 1002 b 1 (where the recesses 1002 b 2are between adjacent protrusions 1002 b 1), where the varying recessdepth defines curved groove plane GP. FIG. 10C is a sectional view cutacross a row of protrusions 1002 b 1, illustrating that end recesses1002 b 2 e are deeper than recesses 1002 b 2, thereby defining thecurved groove plane. The curved groove plane GP illustrated in FIGS.10A-10C extends from front edge 1002 d of working surface 1002 b to backedge 1002 e of working surface 1002 b (and not from side edge 1002 f 1to side edge 1002 f 2).

While FIGS. 9A and 10A illustrate a curved groove plane GP, otherconfigurations are contemplated where the recess/groove depths aredeeper adjacent the front and back edges and shallower at the center ofthe working surface. For example, the grooves could follow an angled, asopposed to a curved, profile.

While the groove plane GP is illustrated as curving along the front toback direction (i.e., from the front edge of the working surface to theback edge of the working surface), the groove plane GP could extend fromone side edge of the working surface to the other side edge of theworking surface. Further, the working surface of the ribbon bonding toolcould have a curved (or varying depth) groove plane that extends in boththe front to back direction (as in FIG. 9A) and in the side to sidedirection (not shown). That is, a depth of the plurality of recessesfollows a profile such that a depth of the recesses is shallower at acentral portion of the working surface, and increases in each directionextending toward a periphery of the working surface.

While FIGS. 9A and 10A-10C illustrate ribbon bonding tools including acurved groove plane, the bottom surface of the tool continues to besubstantially flat (i.e., extending along plane “BSP” shown in FIGS. 9Aand 10C). Ribbon bonding tools having a flat bottom surface may sufferfrom a number of deficiencies. In certain configurations of the presentinvention (e.g., as shown in FIGS. 12A-12B and 14) it may be desirablethat the bottom surface be curved (or otherwise be varied along itslength).

Referring to FIGS. 11A-11B, portions of conventional ribbon bonding tool1102 are shown. As is understood by those skilled in the art, in orderto generate the front to back scrub (in a direction along the length ofthe ribbon material) desired for forming ribbon bonds, tip portion 1102a rotates about its first transverse vibration node N, located adistance L from working surface 1102 b. This distance L is dependent onvarious factors such resonant frequency, tool material characteristics,etc. Exemplary distances L (and therefore the radius) are between 2-15mm, 2-10 mm, and 3-5 mm. A standard bond tool has a flat bottom surfacethat undesirably imparts significant vertical vibration to the bondsurface. More specifically, during the rotation about node N, front andback corners 1150, 1152 fall below the level of the bottom surface inits resting state. A potential consequence is that the corners 1150,1152 generate a vertical vibration or force oscillation in the worksurface.

FIGS. 12A-12B illustrates tip portion 1202 a of a ribbon bonding toolwhich includes working surface 1202 b. The bottom surface of the ribbonbonding tool has a curved profile from front edge 1202 d to back edge1202 e in order to minimize or eliminate vertical excitation of a bondsurface during bonding. The radius of the curved profile may beconfigured as desired. In the illustrated example, the radius R isdesigned to be equal to the distance L between the bottom surface of thetip portion and the location of the first node N. That is, because thebottom surface is shorter at its edge portions, it is less likely tocause the excitation problems associated with conventional tools havinga flat bottom surface.

Although FIGS. 12A-12B are illustrated as including a curved profile theentire length of the working surface from the front edge to the backedge, the present invention is not limited thereto. Any of a number ofconfigurations are possible wherein the working surface extends lower ina center region than (1) at a first surface region extending from afirst edge of the working surface toward the center region, and (2) at asecond surface region extending from a second edge of the workingsurface toward the center region. For example, the first and secondsurface regions may be chamfered, curved, etc. so long as the areasadjacent the first and second edge are shorter than the center areabetween the first edge and the second edge. For example, the first andsecond surface regions may be at least 25% of a length of the workingsurface from the first edge to the second edge. In such an embodiment,the total percentage of the length from the first edge to the secondedge that has a reduced length/height is at least 50% (where theremainder of the working surface, such as the center portion, may beflat).

FIGS. 12A-12B relate to examples of the present invention where thebottom surface follows a curved profile in a direction from the frontedge to the back edge in order to address the potential verticalexcitation problem caused by the rotation of the ribbon bonding toolabout the node. However, conventional tools having a flat workingsurface suffer from other deficiencies. For example, FIG. 13 illustratesa front view of tip portion 1300 a of a ribbon bonding tool. Thus, frontedge 1302 d is shown extending between side edge 1302 f 1 to side edge1302 f 2. As will be appreciated by those skilled in the art, bondinglocations (e.g., die pads) are often tilted or not flat. If the surfaceof the bonding location is excessively tilted, ribbon bond formationwill be uneven. In extreme cases, the ribbon bonding tool could sinkcompletely through the ribbon on one side, touching the fragile die.FIG. 13 illustrates a tilted bonding location 1310 (e.g., a tilted diepad on a semiconductor die). In this illustration, tip portion 1300 a ofthe ribbon boning tool is pressed through most of portion 1312 a ofribbon 1312. Thus, it is possible that a portion of working surface 1302b adjacent side edge 1302 f 2 (e.g., the corner) could contact anddamage bonding location 1310.

FIG. 14 illustrates a front view of tip portion 1400 a of a ribbonbonding tool. Thus, front edge 1402 d is shown extending between sideedge 1402 f 1 and side edge 1402 f 2. Unlike working surface 1302 billustrated in FIG. 13 (which is flat), working surface 1402 b of tipportion 1400 a follows a curved path between side edge 1402 f 1 and sideedge 1402 f 2. Such a curved path tends to minimize the impact ofbonding location tilt (e.g., die tilt) on ribbon bond formation. Whilesuch a curved working surface may result in weaker bonding on theoutside edges of the ribbon material, the curvature may be designed foran application to provide adequate bonding results. Thus, while thecurved surface will tend to result in a variation of the bond strength(e.g., biased to one side) overall bond consistency should improve.Additionally, there is a reduced potential for contact between a portion(e.g., corner) of the ribbon bonding tool and the die or other bondinglocations. The height difference h between a side edge and a centerpoint between the side edges may be between, for example, 1-10 mils, butof course may vary considerably based on the application.

Although FIG. 14 illustrates a curved profile from side edge 1402 f 1 toside edge 1402 f 1, the present invention is not limited thereto. Any ofa number of configurations are possible wherein the working surfaceextends lower in a center region than (1) at a first surface regionextending from a first side edge of the working surface toward thecenter region, and (2) at a second surface region extending from asecond side edge of the working surface toward the center region. Forexample, the first and second surface regions may be chamfered, curved,etc. so long at the areas adjacent the first and second edge are shorterthan the center area between the first edge and the second edge. Forexample, the first and second surface regions may be at least 25% of alength of the working surface from the first side edge to the secondside edge.

As illustrated in FIG. 1, ribbon bonding systems may include a ribbonguide (such as guide 104 in FIG. 1) to direct the ribbon material to aribbon bonding tool, and to facilitate ribbon looping. In FIG. 1, ribbonguide 104 directs the ribbon material (e.g., the material of ribbon loop112) under ribbon bonding tool 102. In certain ribbon bondingapplications (e.g., smaller width ribbon applications), the separateribbon guide may not be adequate to consistently position the ribbonwith the desired accuracy.

FIGS. 15A-15B and 16A-16B illustrate tip portions of ribbon bonding toolthat include integrated ribbon guides for guiding the ribbon materialunder the working surface completely external to the ribbon bondingtool. The integrated ribbon guides are designed to assist in the controlof the side-to-side position of the ribbon under the working surface ofthe ribbon bonding tool. Depending on the application, such designs may(or may not) be used in connection with conventional ribbon guides suchas element 104 shown in FIG. 1. The integrated guide will also simplifythe complexity of the bond head setup for a ribbon bonding systembecause the ribbon guide alignment (to the ribbon bonding tool) may beless critical.

Referring specifically to FIGS. 15A-15B, perspective views of tipportion 1502 a of ribbon bonding tool 1502 are provided. Working surface1502 b is defined between two side wall portions 1502 sw 1 and 1502 sw2. Side wall portion 1502 sw 1 is provided along side edge 1502 f 1, andside wall portion 1502 sw 2 is provided along side edge 1502 f 2. Sidewall portion 1502 sw 1 includes tapered/angled side wall 1502 t 1, andside wall portion 1502 sw 2 includes tapered/angled side wall 1502 t 2.As shown in FIG. 15A, side wall portions 1502 sw 1 and 1502 sw 2 extendpartially up to back side 1502 bs. Ribbon material (e.g., part of ribbonloop 1512 shown in FIG. 15B) is guided from a ribbon supply to a pathdefined between side wall portions 1502 sw 1 and 1502 sw 2 to workingsurface 1502 b. Side wall portions 1502 sw 1 and 1502 sw 2 (which extendpartially along back side 1502 bs) channel the ribbon material to thedesired position under working surface 1502 b from back edge 1502 e tofront edge 1502 d. The angled configurations of side wall portions 1502sw 1 and 1502 sw 2 assist in the channeling of the ribbon material. Theheight of side wall portions 1502 sw 1 and 1502 sw 2 is preferably smallenough that the side wall portions do not touch the bond surface undernormal bonding conditions. The width between side wall portions 1502 sw1 and 1502 sw 2 may be substantially the same as the width of the ribbonmaterial being bonded, considering manufacturing tolerances of theribbon material.

Referring specifically to FIGS. 16A-16B, perspective views of tipportion 1602 a of ribbon bonding tool 1602 are provided. Side wallportions 1602 sw 1 and 1602 sw 2 extend along a portion of back side1602 bs of ribbon bonding tool 1602. Side wall portion 1602 sw 1includes tapered/angled side wall 1602 t 1, and side wall portion 1602sw 2 includes tapered/angled side wall 1602 t 2. As shown in FIG. 15A,side wall portions 1602 sw 1 and 1602 sw 2 extend partially down toworking surface 1602 b. Ribbon material (e.g., part of ribbon loop 1612shown in FIG. 16B) is guided from a ribbon supply to a path definedbetween side wall portions 1602 sw 1 and 1602 sw 2 to working surface1602 b. Side wall portions 1602 sw 1 and 1602 sw 2 channel the ribbonmaterial to the desired position under working surface 1602 b from backedge 1602 e to front edge 1602 d. The angled configurations of side wallportions 1602 sw 1 and 1602 sw 2 assist in the channeling of the ribbonmaterial. If the side wall portions 1602 sw 1 and 1602 sw 2 extendpartially along working surface 1602 b, then the height of at least thatportion of side wall portions 1602 sw 1 and 1602 sw 2 is preferablysmall enough that the side wall portions do not touch the bond surfaceunder normal bonding conditions. As with FIGS. 15A-15B, the widthbetween side wall portions 1602 sw 1 and 1602 sw 2 may be substantiallythe same as the width of the ribbon material being bonded, consideringmanufacturing tolerances of the ribbon material.

The various exemplary ribbon bonding tools disclosed herein may havevarying characteristics. For example, while certain of the drawingsdisclose the working surface as being substantially planar (e.g., FIGS.12A-12B, FIG. 14, FIGS. 15A-15B, and FIGS. 16A-16B), it is understoodthat any of the tools may have a working surface with a waffle or gridconfiguration or other configuration defining a plurality of protrusionsand recesses (e.g., such as shown in others of the drawings). FIG. 17 isa perspective view of a portion of working surface 1702 b of aconventional ribbon bonding tool, where working surface 1702 b defines aplurality of protrusions 1702 b 1 (and recesses as illustrated) in awaffle type configuration. Protrusions 1702 b 1 define sharp edges SEwhich undesirably can damage the ribbon material being bonded, and mayundesirably contribute to build-up of ribbon material in the wafflepattern. FIG. 18 is a perspective view of a portion of working surface1802 b of an inventive ribbon bonding tool, where working surface 1802 bdefines a plurality of protrusions 1802 b 1 (and recesses asillustrated) in a waffle type configuration. In contrast to sharp edgesSE in FIG. 17, protrusions 1802 b 1 define rounded edges RE. Forexample, corners of protrusions/teeth 1802 b 1, may be rounded if theyare sharper than 1 mil, with a maximum of 2 mils.

Various embodiments of the present invention include features on oradjacent the working surface of a ribbon bonding tool including, forexample, protrusions/teeth, recesses/grooves, rounded edges, side wallsportions, amongst others. Such features may be formed by various methods(e.g., using computer control) including, for example, laser-machining,fluid-jet milling, direct molding, mechanical grinding, or EDM(electrical discharge machining).

Although the present invention includes the aforementioned features(e.g., protrusions/teeth, recesses/grooves, rounded edges, side wallsportions) having exemplary shapes/dimensions, it is understood thatalternative shapes/dimensions are contemplated.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

What is claimed:
 1. A ribbon bonding tool comprising: a body portionincluding a tip portion, the tip portion including a working surfacebetween a front edge of the tip portion and a back edge of the tipportion, the working surface including a region defining a grid patternof a plurality of recesses and a plurality of protrusions, the workingsurface also defining (a) a first planar portion between the region andthe front edge of the tip portion, and (b) a second planar portionbetween the region and the back edge of the tip portion, wherein alength of the working surface is defined between the front edge and theback edge, and wherein each of the first planar portion and the secondplanar portion extends along between 20-40 percent length.
 2. The ribbonbonding tool of claim 1 wherein the working surface also defines (c) athird planar portion between the region and a first side of the tipportion, and (d) a fourth planar portion between the region and a secondside of the tip portion.
 3. The ribbon bonding tool of claim 1 whereinthe region defining the plurality of recesses and the plurality ofprotrusions is a waffle pattern of protrusions and recesses.
 4. Theribbon bonding tool of claim 3 wherein the protrusions have roundededges.
 5. The ribbon bonding tool of claim 1 wherein the region definesa plurality of protrusions extending above a planar surface of theworking surface.
 6. The ribbon bonding tool of claim 5 wherein theplurality of protrusions are round.
 7. The ribbon bonding tool of claim5 wherein the plurality of protrusions are rectangular.
 8. The ribbonbonding tool of claim 5 wherein the plurality of protrusions are diamondshaped.
 9. The ribbon bonding tool of claim 5 wherein the plurality ofprotrusions are arranged in at least one row.
 10. The ribbon bondingtool of claim 5 wherein the plurality of protrusions are arranged in atleast two rows.
 11. The ribbon bonding tool of claim 5 wherein theplurality of protrusions include rounded edges.
 12. The ribbon bondingtool of claim 1 wherein the region defines a plurality of recessesextending below a planar surface of the working surface.
 13. The ribbonbonding tool of claim 12 wherein the plurality of recesses are round.14. The ribbon bonding tool of claim 12 wherein the plurality ofrecesses are rectangular.
 15. The ribbon bonding tool of claim 12wherein the plurality of recesses are diamond shaped.
 16. The ribbonbonding tool of claim 12 wherein the plurality of recesses are arrangedin at least one row.
 17. The ribbon bonding tool of claim 12 wherein theplurality of recesses are arranged in at least two rows.
 18. A ribbonbonding system comprising: (a) a ribbon bonding tool including a bodyportion including a tip portion, the tip portion including a workingsurface between a front edge of the tip portion and a back edge of thetip portion, the working surface including a region defining a gridpattern of a plurality of recesses and a plurality of protrusions, theworking surface also defining (a) a first planar portion between theregion and the front edge of the tip portion, and (b) a second planarportion between the region and the back edge of the tip portion, whereina length of the working surface is defined between the front edge andthe back edge, and wherein each of the first planar portion and thesecond planar portion extends along between 20-40 percent of the length;(b) a conductive ribbon material configured to be bonded between bondinglocations to form an interconnection; and (c) an ultrasonic transducerfor carrying the ribbon bonding tool, and for causing scrubbing motionat the tip portion of the ribbon bonding tool for bonding the conductiveribbon material to the bonding locations to form the interconnection.